A widely used system of supplying medical oxygen to patients with impaired respiratory tracts, but who desire mobility, is composed of small tanks ranging from 160 to 660 liters at pressures of 2,000 to 3,000 PSI. The tanks are equipped with a valve that is manually opened or closed and which contains an over-pressure release device, usually a rupture disk. The prior art design of the most widely used valve of this type is shown in FIG. 8. Such valves are constructed of brass or stainless steel. The combined weight of an oxygen cylinder and the valve poses a considerable burden to the elderly or the infirm who make use of these devices typically by transporting the cylinders in shoulder bags or two-wheeled carts.
The valve shown in FIG. 8 does not allow "soft" opening or pressurization. Rather, it permits high pressure oxygen to adiabatically recompress when it enters downstream regulators, which may cause rapid temperature rises that are unsafe. Such temperature rises range from 500 degrees Fahrenheit to 1,600 degrees F. Further, the threads on the operating stem are disposed in the flow path of the high pressure fast moving oxygen stream which permits particulates generated by thread contact to be swept into downstream devices such as regulators. Fires have been known to occur in oxygen regulators as a result of the recompression problem of the prior art valve coupled with the presence of particulates that will combust when exposed to a pure or high oxygen environment. What is needed is an improved valve design that is light weight, requires a lower torque to operate, requires fewer components, prevents particulate contamination of the gas flow, minimizes unswept internal areas, provides a "soft" or metered opening of the valve and has no metal to metal contact in the internal passages of the valve.